The High Speed screw is set to"0". The HIGH SPEED SCREW has a plastic cap on it. The Low Speed screw is set to 1 1/2.The LOW SPEED SCREW has a pin through it.
I hope this helps.
The plastic cap is on the high speed to prevent it from being set to more than 1/4 turn out. It should be set to "0". Be sure both carbs are the same and in sync.